Run the smoke tests against the packed package

[cristianrgreco]

Summary

The smoke tests now run against the package as it is published, with only its production dependencies installed.

A new smoke-test-setup action does the setup for both smoke-test jobs:

1. Builds and packs packages/testcontainers.
2. Runs npm ci --omit=dev --workspace packages/testcontainers, which installs only the package's production dependencies, at the versions in package-lock.json.
3. Moves that node_modules into an empty project in the runner's temp directory and replaces the workspace link with the unpacked tarball.
4. Copies the smoke-test files there and returns the directory as its path output.

The jobs then run the smoke tests from that directory. Other changes:

• smoke-test.js, smoke-test.mjs and smoke-test.jest.js import testcontainers by name instead of ./build/index. They still run from the repository after a build, because the workspace link resolves the name to build/index.js.
• The npm prune --omit=dev step is removed.

Why

The prune step never produced a production-only environment. Measured locally, it removes 11 packages (the package's @types/* dev dependencies) and leaves about 325 installed, including vitest, TypeScript and Biome from the root. And because the tests imported ./build/index from inside the repository, they never went through the package's main entry or its files list.

Dependency versions are unchanged: they still come from package-lock.json, so a run is reproducible and can't fail because of a new upstream release.

Verification

The action's two scripts were run locally, verbatim, in a copy of the repository installed the way the job installs it:

• The empty project has 172 packages. Every one is at its package-lock.json version and none is dev-only. vitest, TypeScript, Biome and shx are absent.
• node_modules/testcontainers is a real directory holding the tarball's files (build, package.json, README.md, LICENSE), plus the two dependencies the lockfile nests under the package (undici, get-port).
• With Docker, from that project: node ./smoke-test.js and node ./smoke-test.mjs exit 0, and the Jest smoke test passes (1 test).
• Red checks, each against the same project:
  • "main" pointed at a missing file: fails with Please verify that the package.json has a valid "main" entry. The old test's import of ./build/index still loads in that state.
  • A production dependency (byline) removed: fails with Cannot find module 'byline'.
• npm run format, npm run lint: no fixes applied.
• Not run locally: the Bun steps, since Bun isn't installed here. CI covers them.

Related PRs

• Share one dependency cache across CI jobs #1497 edits the line directly above the changed steps in both jobs, so whichever merges second will need a small conflict resolved.
• Detect unused code and dependencies with knip #1492 adds knip. Once both are merged, its knip.jsonc entry for packages/testcontainers needs to change from smoke-test.jest.js to smoke-test.*, because the workflow no longer references the other two files by their repository path. Checked locally with Detect unused code and dependencies with knip #1492's config: with that entry, knip reports nothing for the smoke tests.

Why this isn't breaking

CI and smoke-test files only. The smoke-test files aren't published (files is ["build"]), and no package source or dependency changes.